This disclosure is related to a switch fabric topology, such as may be implemented on a packet switched backplane.
A switch fabric, e.g., arrangements or configurations of devices that, for example, handle, process, route, and/or transfer information, may typically interconnect or mutually couple network equipment, such as, for example, switches, servers, network appliances, local area networks (LANs) and/or wide area networks (WANs). Such switch fabrics may affect or control information flow within a network, such as between network equipment, located, for example, within reasonable proximity. Typically, such switch fabrics are implemented within a self-contained unit, such as a shelf or chassis, for example, with a backplane. The shelf may have slots or other compartments where one can plug-in or otherwise physically and electrically couple servers, switches, routers, telco line I/O cards, etc., of the network with the backplane.
When selecting a packet switched backplane topology for a switch fabric, there are several commonly used backplane topologies, although, of course, other configurations or topologies are also possible. These backplane topologies may include, for example, a star topology, a mesh topology and/or a cascaded mesh topology, illustrated, for example, in FIGS. 4, 5, and 6, respectively.
In a typical star topology, as illustrated in FIG. 4, the nodes of the network couple through a switch fabric to an active switch fabric device. If two switch fabric devices are employed, for redundancy typically, then the configuration is referred to as a dual star topology. FIG. 4 is a schematic diagram illustrating an embodiment of a dual star backplane topology for a network having 16 nodes. The switch fabric device or devices may control the transfer or redirection of signals through the switch fabric from at least one of the network nodes to at least another of the network nodes or to external equipments/networks through uplink ports or management ports.
In a mesh topology, in contrast, the network nodes are coupled to directly via the backplane. The nodes include a switching circuit so that a dedicated switch fabric device may be omitted. As the number of nodes increases, however, the complexity of the bus increases significantly. FIG. 5 is a schematic diagram illustrating a mesh backplane topology for a network having 17 nodes, for example.
With a cascaded mesh topology, the nodes of the network may be divided into subsets or smaller meshes, where the nodes of a subset are coupled directly through a backplane. One or more nodes in one subset may then be coupled to one or more nodes in a second subset via a switch fabric device or directly through the backplane. Thus, with this particular topology, an upper bound is present on the number of ‘node hops’ it takes to route signals between any two nodes in the network. Also this topology results in fewer interconnects.
Although, in general, these backplane topologies individually may have different advantages and disadvantages, typically, adjustments in the network configuration may make it desirable to have a previously selected backplane topology removed and replace it with another or different backplane topology. This, however, in many situations, may prove disadvantageous because it may increase cost, make the network unavailable for a time, and/or increase network complexity.